I will give a brief overview of mathematical models of visual processing in the brain, both in the retina and in the visual cortex. I will then discuss some recent results demonstrating how certain motion illusions can arise from models of non-linear processing in the retina.

The Ouchi Illusion and the Out-of-focus Illusion are stationary images which can produce a perception of motion or "jittering" under certain conditions. These effects are related to small unconscious eye movements, which are ubiquitous in humans and play an important role in human vision. Since we do not normally perceive motion in the world during these eye movements, there must be a mechanism to compensate for the motion of the visual scene across the retina. I will present a computational model of visual processing which compensates for eye-motion under normal viewing conditions. In this model, the effect of the Ouchi and Out-of-focus illusions are predicted as failure modes of the compensation mechanism.